1. Field of the Invention
This invention relates to an engine valve operating system for an internal combustion engine, arranged to control the valve timing and the amount of valve lift of an intake or exhaust valve in accordance with engine operating conditions.
2. Description of the Prior Art
A variety of engine valve operating systems have been heretofore proposed to control the valve timing and the amount of valve lift of intake or exhaust valves of an internal combustion engine. Of these systems, there is one of the type wherein valve actuating effort is transmitted to the intake or exhaust valve through a rocker arm which is in fulcrum contact with a lever or fulcrum member. The fulcrum member is pivotal at its one end and whose pivotal location is controlled by a control cam which is driven in accordance with engine operating conditions.
However, in case where this type engine valve operating system is applied to a multi-cylinder engine having a plurality of the control cams mounted on a single camshaft, a greater torque due to reaction force of a valve spring always acts on the camshaft since any of the intake or exhaust valve makes its lift operation. Rotating the camshaft against the greater torque degrates response of the control cam while requiring a large capacity and sized actuator for the camshaft.